Methods for improving angled line feature accuracy and throughput using electron beam lithography and electron beam lithography system

ABSTRACT

Methods to reduce the write time for forming mask patterns having angled and non-angled features using electron beam lithography are disclosed. In one exemplary embodiment, non-angled features of the mask pattern are formed by exposure to an electron beam. The orientation of the substrate and a path of the generally rectangular-shaped shot from the electron beam may be relatively altered such that the substrate is exposed to the electron beam to form the angled features as if they were non-angled features. In another exemplary embodiment, the electron beam lithography system determines whether it is necessary to relatively alter the orientation of the substrate and a path of the generally rectangular-shaped shot from the electron beam to form the angled features based on the number of angled features and the time required for relatively altering the orientation. Electron beam lithography systems employing a rotatable stage, rotatable apertures, or both are disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 10/824,279,filed Apr. 14, 2004, pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the processing of substrates such assemiconductor wafers using electron beam lithography. More specifically,the present invention relates to methods for forming a mask pattern on aresist using electron beam lithography such that write time is reduced.

2. State of the Art

Semiconductor devices including integrated circuitry, such as memorydice, are mass produced by fabricating hundreds or even thousands ofcircuit patterns on a single semiconductor wafer or other bulksemiconductor substrate using lithographic processing in combinationwith various other processes. In order to increase the number of memorycells on semiconductor memory devices for a given surface area, it isimportant to accurately control the resolution of the images producedduring lithography. These images are used to define structural featureson a semiconductor substrate in fabricating the integrated circuitry ofsuch semiconductor memory devices.

Photolithography is a process in which a pattern is delineated in alayer of material, such as a photoresist, sensitive to photons. Inphotolithography, an object containing a pattern (e.g., reticle or mask)is exposed to incident light. The image from the reticle or mask isprojected onto a photoresist that covers a semiconductor wafer or othersubstrate. The photolithographic process typically involves exposing anddeveloping the photoresist multiple times. At a given step, thephotoresist is selectively exposed to photons and then developed toremove one of either the exposed or unexposed portions of photoresist,depending on whether a positive or negative photoresist is employed.Complex patterns typically require multiple exposure and developmentsteps.

Currently, conventional photolithography using light is only capable ofproducing structural features of about 100 nm in minimum dimension. Thisinadequacy limits the ability of a manufacturer to produce extremelysmall structural features for integrated circuits through conventionalphotolithography processes. A capability to further reduce thedimensions of structural feature size is particularly important to thefabrication of semiconductor memory devices to enable increasing thenumber of memory cells on such semiconductor memory devices of a givensize.

In order to produce structural features smaller than the capability ofphotolithography, electron beam lithography (EBL) has been developed.EBL produces a desired pattern on a resist by irradiating a resistsensitive to electrons with an appropriate amount of electrons onspecific portions of the resist. In a typical variable shaped vectorscan EBL process, the electron beam emitter is positioned over onlyspecific sites of the resist and the resist is exposed to a shaped beamof electrons, called a shot. Positioning is accomplished by acombination of movement of the substrate stage in the x-y direction inthe plane of the substrate and/or movement of the electron beam. Thus,the pattern data used by the EBL system must be provided withinformation that includes both the dose of electrons and the position ofeach site on the resist to be exposed for each shot.

The typical variable shaped vector scan EBL process decomposes a patterninto rectangular-shaped or forty-five degree angle triangular shaped“primitives.” The rectangles are aligned along the x-y axes in the planeof the substrate defining the vector scan. The forty-five degree angletriangular shaped primitives are only capable of exposing featurespositioned at a forty-five degree angle without using an excessivenumber of shots. The electron beam from the EBL system is capable ofexposing a primitive in a single shot. As shown in FIGS. 1A and 1B, fora typical vector scan, a substantial portion of the pattern is made upof triangles approximated by various sizes of rectangles while only asmall portion of the pattern is made up of true rectangles. Because thewrite time is proportional to the number of shots, this use of smallrectangles to approximate triangles requires a great number of shots andtakes up to 90% of the exposure time. Furthermore, it results in loss offidelity of the mask pattern produced on the resist as shown by thestepped edges in the triangular regions in FIGS. 1A and 1B.

Due to the long exposure times inherent in using small rectangles toapproximate triangles, cell projected EBL may be used. In cell projectedEBL, a variable shaped electron beam, typically having the shape of thedesired cell pattern or the shapes at various angles, is used to producethese non-rectangular shapes. The variable shape is produced by passingthe electron beam through an aperture having the desired shape. When avariable shaped beam is used, the pattern data used by the EBL systemincludes the dose of electrons, location, size, and shape for each shot.Although cell projected EBL reduces the write time required to expose apattern, the total throughput is still undesirably too long. Also, it isdifficult to prepare enough non-rectangular shaped apertures toaccommodate the multitude of patterns an integrated circuit designer maydesire to use. Furthermore, using multiple apertures of varying shapescauses difficulties in the beam alignment and calibration of the EBLsystem. Examples of apparatus and methods for variable shaped EBL areshown in U.S. Pat. No. 6,573,516 to Kawakami, U.S. Pat. No. 6,455,863 toBabin et al., U.S. Pat. No. 6,259,106 to Boegli et al., U.S. Pat. No.5,760,410 to Matsuki et al., and U.S. Pat. No. 4,532,598 to Shibayama etal. each of the disclosures of which are herein incorporated byreference for all they disclose.

The problem with write time is exacerbated by the new generation ofintegrated circuit designs that use “angled line” features as shown byFIG. 2. In FIG. 2, the exposed regions 202 (dark) are the resist regionsthat have been exposed to the shots of an electron beam from an EBLsystem. The exposed regions 202 are made up individual shots ofprimitive rectangles 206 which form the angled features on the resist.The exposed regions 202, otherwise known as the angled line features,are formed by using multiple stepped, or partially offset, rectangularshots. The exposed regions 202 exhibit a loss of fidelity as shown bythe stepped edges 208 which form the angled features. The loss offidelity in the mask pattern is an artifact of the processing becausethe exposed region 202 would, ideally, exhibit smooth linear edges asrepresented by the design data for the integrated circuit layout. Thelighter regions 204 are the unexposed regions of resist. In order toincrease the number of memory cells on semiconductor memory devices fora given surface area, integrated circuit designers lay out the featuresat a certain angle to maximize the use of the substrate surface area.However, this “angled line” layout makes it more expensive to generatethe pattern on the resist because of the numerous non-rectangular shapesthat must be used to form the pattern, resulting in undesirably longwrite times and the great number of rectangular shots from the electronbeam required to form the angled features.

Accordingly, a need exists to develop a method for generating angledfeatures on resist using electron beam lithography wherein the writetime is reduced compared to conventional EBL methods. Another needexists for a method to modify conventional EBL systems such that themethod may be implemented by modification of a semiconductormanufacturer's existing equipment.

BRIEF SUMMARY OF THE INVENTION

The present invention, in a number of embodiments, includes electronbeam lithography (EBL) systems and methods to shorten the write timerequired to produce mask patterns on a resist having angled featuresusing EBL. The present invention may be used in EBL processing forfabrication of semiconductor devices, liquid crystal display elements,thin-film magnetic heads, reticles, and for many other applications thatrequire accurate mask pattern generation.

An exemplary EBL system is disclosed. The EBL system includes anelectron gun capable of emitting an electron beam and at least one lenslocated for the electron beam to pass therethrough. The EBL system alsoincludes a first aperture located for the electron beam to passtherethrough and at least one deflector for deflecting the electron beamthrough a second aperture to define a generally rectangular shape for anelectron beam shot therethrough. A projection lens receives the electronbeam from the second aperture to project the electron beam onto asubstrate held by a movable stage. In an exemplary embodiment, themovable stage, the at least two apertures in combination, or both, maybe rotatable with respect to one another and the position thereofaccurately determined by a controller.

An exemplary embodiment for forming a mask pattern on a resist is alsodisclosed. The mask pattern to be formed includes at least onenon-angled feature and at least one angled feature oriented at apredetermined angle relative to the non-angled feature. A substrate,such as a semiconductor wafer or a glass-based material, having a resistdisposed thereon and located to receive an electron beam is provided.The resist is then exposed using at least one generallyrectangular-shaped shot from an electron beam to form at least onenon-angled feature. A rotational orientation of the substrate and thegenerally rectangular shape of the electron beam shot may be relativelyaltered with respect to each other by the predetermined angle. Then, theresist is again exposed to at least one additional generallyrectangular-shaped shot from the electron beam to form at least oneangled feature, the angled feature having at least one linear,peripheral edge oriented at the predetermined angle relative to thenon-angled feature. Thus, the angled features are exposed as if theywere non-angled features using only generally rectangular-shapedelectron beam shots. This reduces the total write time for forming themask pattern and produces a mask pattern wherein the angled andnon-angled features exhibit smooth edges.

Another exemplary embodiment for forming a mask pattern on a resist isdisclosed. The mask pattern to be formed includes at least onenon-angled feature and at least one angled feature oriented at apredetermined angle relative to the non-angled feature. A substrate,such as a semiconductor wafer or a glass-based material, having a resistdisposed thereon and located to receive an electron beam is provided. Analgorithm is used to determine whether the time required to form the atleast one angled feature using multiple stepped or offsetrectangular-shaped shots is greater than or less than the time requiredto relatively alter a rotational orientation of the substrate and thegenerally rectangular shape of the electron beam shot with respect toeach other by the predetermined angle and subsequently form the at leastone angled feature. The determination is based, in part, on the numberof angled features, the number of shots required to form the angledfeature, and the time required for relatively altering the rotationalorientation of the substrate and the generally rectangular shape of theelectron beam. If the time to alter the rotational orientation of thesubstrate and the generally rectangular shape of the electron beam shotrelative to each other by the predetermined angle plus form the angledfeatures is greater, the mask pattern is formed by exposing the at leastone angled feature and the at least one non-angled feature withoutrelatively altering the orientation of the substrate and the generallyrectangular shape of the electron beam shot using generallyrectangular-shaped shots from an electron beam. If the algorithmdetermines that it is more time efficient, the at least one non-angledfeature is exposed using at least one generally rectangular-shaped shotfrom an electron beam followed by relatively altering a rotationalorientation of the substrate and the generally rectangular shape of theelectron beam shot with respect to each other by the predetermined angleand subsequent exposing of the at least one angled feature using atleast one generally rectangular-shaped shot from an electron beam. Theabove exemplary embodiment enables optimization of the write time forforming mask patterns. If the substrate and the generally rectangularshape of the electron beam shot are re-oriented with respect to eachother by the predetermined angle to form the angled features, the angledfeatures are exposed as if they were non-angled features using onlygenerally rectangular-shaped electron beam shots. Furthermore, thisreduces the total write time for forming the mask pattern and produces amask pattern wherein the angled and non-angled features exhibit smoothedges.

These features, advantages, and alternative aspects of the presentinvention will be apparent to those skilled in the art from aconsideration of the following detailed description taken in combinationwith the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, which illustrate what is currently considered to be thebest mode for carrying out the invention:

FIGS. 1A and 1B are illustrations of using rectangular-shaped primitivesto form the triangular portions of a mask pattern using conventionalelectron beam lithography.

FIG. 2 illustrates a mask pattern having angled features processed usingelectron beam lithography.

FIGS. 3A and 3B illustrates exemplary electron beam lithography systemsof the present invention that may be used to implement the methods ofthe present invention.

FIG. 4 illustrates a portion of a mask pattern of a simplifiedintegrated circuit layout containing angled and non-angled features.

FIG. 5 is a process flow diagram of an exemplary embodiment of thepresent invention.

FIG. 6 illustrates the angled features of a mask pattern formed by theelectron beam lithography method of the present invention.

FIG. 7 is a process flow diagram of another exemplary embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention, in a number of embodiments, includes electronbeam lithography (EBL) systems and methods to shorten the write timerequired to produce mask patterns on a resist having angled featuresusing EBL. The present invention may be used in EBL processing forfabrication of semiconductor devices, liquid crystal display elements,thin-film magnetic heads, reticles, and for many other applications thatrequire accurate mask pattern generation.

The present invention employs commercially available EBL systems thatare modified to include a stage rotatable about an axis perpendicular tothe stage, rotatable apertures, or both. For instance, commerciallyavailable variable shaped electron beam, vector scan EBL systems, suchas the NuFlare Technology EBM4000 system and the JEOL JBX-9000 systemmay be modified to successfully practice the methods of the presentinvention.

FIG. 3A shows the configuration of an exemplary electron-beamlithography system 300 which may be used to practice the presentinvention. FIG. 3 discloses a processor 1, a magnetic disk 2, and amagnetic tape drive 3. These units are interconnected over a bus 4, andconnected to a data memory 6 and stage control circuit 7 via aninterface circuit 5 over the bus 4. A housing (column) 8 accommodates anelectron gun 9, a lens 10, a blanking electrode 11, a first aperture 30,a lens 12, a shaping deflector coil 13, a second aperture 32, asub-deflector coil 14, a projection lens 15, a main deflector coil 16, astage 17, and a substrate 18. The first aperture 30 and the secondaperture 32 may be termed, collectively, an apparatus for defining ashape for the electron beam shots from the electron gun 9 therethrough.The substrate 18 is placed on the stage 17. The stage 17 may be moved inthe X and Y directions defining the plane of the stage 17 and rotated asshown by arrow R about a Z axis that is substantially perpendicular tothe surface of the stage 17 (illustrated by the X-Y-Z coordinate systemin FIG. 3A) according to an output signal of the stage control circuit7. The position of stage 17, whether translated in the plane of thestage 17 or rotated about a Z axis perpendicular to the surface of thestage 17, may be accurately determined by a laser interferometer 28.Laser interferometer 28 may be in communication with the stage controlcircuit 7 such that the positional information of the stage 17, asdetermined by the laser interferometer 28, may be sent to the stagecontrol circuit 7.

Referring to FIG. 3B, another exemplary EBL system 300′ is illustratedwherein the first aperture 30 and the second aperture 32 comprises anapparatus that may be angularly rotated in combination as shown by arrowR about a Z axis that is coaxial with the electron beam. The rotation ofthe first aperture 30 and the second aperture 32 may be accuratelycontrolled by a rotation mechanism 31. The rotation mechanism 31 mayinclude an aperture support (not shown) that holds the first aperture 30and the second aperture 32 and a drive to initiate and control rotationthereof. The drive may include reduction gearing for extremely preciserotation over a selected arc. The aperture support may be fixed to thehousing 8. The first aperture 30 and the second aperture 32 are rotatedby the same angle such that the alignment of the apertures with respectto one another is not altered after the rotation thereof. The rotationalposition of the first aperture 30 and the second aperture 32 may bedetermined by a laser interferometer 28′ that communicates thepositional information to an aperture position control circuit 36. Thedrive may, alternatively, be a rotary stepper motor or include a rotaryencoder for accurate determination of the positional information of thefirst aperture 30 and the second aperture 32 to be communicated to theaperture position control circuit 36.

Data read from the data memory 6 is supplied to a pattern correctioncircuit 20 via a pattern generation circuit 19. The pattern correctioncircuit 20 applies a blanking signal to the blanking electrode 11 via anamplifier 21. Moreover, the pattern correction circuit 20 applies asignal to the coils 13, 14, and 16 via digital-to-analog converters(DAC) 22, 24, and 26 and amplifiers 23, 25, and 27.

Again with continued reference to FIGS. 3A and 3B, the operation of EBLsystems 300 and 300′ are described. An electron beam emitted from theelectron gun 9 passes through the lens 10. The electron beam is thentransmitted or intercepted by the blanking electrode 11, and reshapedinto a rectangular beam of parallel rays having any spot size of, forexample, 3 μm or less by passing through a rectangular-shaped firstaperture 30. After passing through the first aperture 30, the shapingdeflector 13 deflects the electron beam having a generally rectangularshape to overlap a portion of the second aperture 32 to form a smallergenerally rectangular-shaped electron beam. This enables forming avariable shaped electron beam depending on the amount of overlap of theelectron beam deflected by shaping deflector 13 and the second aperture32. Differently shaped or additional apertures may be used in EBL system300 and 300′ to produce an angled shape, such as a forty-five degreetriangle, in addition to rectangular or square shapes. The sub-deflectorcoil 14, and main deflector coil 16 deflect the electron beam onto thespecific portions of the substrate 18 desired to be exposed to theelectron beam by use of the deflector coils and/or the movement of stage17.

The electron beam is then converged on the surface of the substrate 18through the projection lens 15. Areas where shaping deflector coil 13,sub-deflector coil 14, and main deflector coil 16 can deflect the beamget larger in that order. Specifically, the area where the shapingdeflector coil 13 can deflect the beam is smaller than that where thesub-deflector coil 14 can. The area where the sub-deflector coil 14 candeflect the beam is smaller than area that the main deflector coil 16can. For ensuring a large area where the beam can be deflected, thenumber of windings of a coil must be increased accordingly. The responsespeeds of the coils get lower in reverse order. In other words, asettlement wait time required by the shaping deflector coil 13 is theshortest. Settlement wait times required by the sub-deflector coil 14and main deflector coil 16 get longer in that order. A more detailedexplanation is given by each of the aforementioned U.S. Pat. No.6,573,516 to Kawakami, U.S. Pat. No. 6,455,863 to Babin et al., U.S.Pat. No. 6,259,106 to Boegli et al., U.S. Pat. No. 5,760,410 to Matsukiet al., and U.S. Pat. No. 4,532,598 to Shibayama et al., the disclosuresof each of which are incorporated herein by reference.

FIG. 4 illustrates a simplified portion 400 of a mask pattern to beformed on a resist disposed on a substrate having a first coordinatesystem defined by an X reference axis and a Y reference axis and asecond coordinate system defined by an X′ reference axis and a Y′reference axis, wherein the two coordinate systems are oriented at anangle θ relative to each other. Portion 400 contains non-angled features402 shown, for clarity, with the X and the Y reference axes translatedonto it. Portion 400 also contains angled features 404 shown, forclarity, with the X′ and the Y′ reference axes translated onto it. Theangled features 404 are oriented by an angle θ relative to thenon-angled features 402. The non-angled features 402 and angled features404 may be comprised of primitive shapes such as rectangles 406. Theprimitive shapes, such as rectangles 406, that form the angled features404 do not exhibit a stepped or offset geometry as shown in FIG. 2 ofthe prior art. Instead, the sides of multiple rectangles 406 are abuttedto and aligned with adjacent rectangles 406 to form a larger contiguousangled feature 404. The rectangles 406 used to form the non-angledfeatures 402 each have an edge generally parallel to the X axis and anedge generally parallel to the Y axis. Similarly, the rectangles 406used to form the angled features 404 each have an edge generallyparallel to the X′ axis and an edge generally parallel to the Y′ axis.During EBL processing of a resist to form the mask pattern, which willbe discussed in more detail below, the non-angled features 402 and theangled features 404 are formed on a resist by exposing the resist toshots from the electron beam, wherein the shape, size, and orientationof the electron beam corresponds to the shape, size, and orientation ofeach rectangle 406 of the mask pattern.

An exemplary method that utilizes the EBL systems 300 or 300′ shown inFIGS. 3A and 3B are described with reference to FIG. 4 and the processflow diagram of FIG. 5. The design data for a particular integratedcircuit may be stored in a magnetic storage medium or other suitablestorage device that may be coupled to the processor that controls theEBL system 300 or 300′. Typically, the design data contains bothnon-angled features and angled features which comprise the electronicdevices or components of the integrated circuit. An EBL system 300 or300′ is provided with a movable stage 17 supporting a substrate 18 madefrom a semiconductor material such as a silicon wafer or a galliumarsenide wafer, or a glass material useful for forming a photomask orreticle. Substrate 18 includes a layer of resist material on the surfacethat may be exposed to the electron beam of the EBL system. Suitablepositive EBL resist materials include FEP-171 commercially availablefrom Fuji-Film Arch, PEK-130 commercially available from SumitomoChemical, and ZEP7000 commercially available from Zeon Corporation.Suitable negative EBL resists include FEN-270 commercially availablefrom Fuji-Film Arch and NEB22 commercially available from SumitomoChemical.

In act 502, the design data may be converted to the machine languageused by the particular EBL system. If the design data containsnon-angled features, in act 504 the non-angled features 402 may beformed by exposing the resist to an electron beam shot-by-shot usinggenerally rectangular-shaped shots from the EBL system.

Following exposing of the non-angled features 402, in act 506 therotational orientations of the stage 17 supporting the substrate 18 andthe first aperture 30 and the second aperture 32 may be relativelyaltered with respect to each other by a predetermined angle. In anexemplary embodiment, the stage 17 supporting the substrate 18 may berotated by an angle θ about a Z axis that is perpendicular to thesurface of substrate 18 while the first aperture 30 and the secondaperture 32 remain stationary. In another exemplary embodiment, thefirst aperture 30 and the second aperture 32 may be rotated by an angleθ about a Z axis that is perpendicular to the surface of substrate 18while the substrate 18 remains stationary. The rotation of stage 17 maybe controlled by the laser interferometer 28 operably coupled to thestage control circuit 7 and the processor 1 to accurately control andmeasure the rotation of stage 17. If the first aperture 30 and thesecond aperture 32 are rotated, the rotation may be similarly controlledby the laser interferometer 28′ operably coupled to the apertureposition control circuit 36 to accurately control and measure theposition thereof or a stepper motor or a rotary encoder may be employed.In act 508, the angled features 404 may then be formed by exposing theresist to an electron beam shot-by-shot using generallyrectangular-shaped shots from the EBL system. Since the substrate 18 orthe first aperture 30 and the second aperture 32 has been rotated, theangled features 404 are exposed on the resist by the EBL system as ifthey were non-angled features.

Thus, the angled features 404 may be written out using only generallyrectangular-shaped shots. The shots may be larger and there are notriangular regions that must be composed of multiple rectangular shots.Therefore, the number of shots required to produce angled features ofthe mask pattern is reduced, resulting in a shorter write time.Furthermore, the multiple shots from the electron beam do not exhibit astepped, or offset, geometry. Instead, the sides of multiple rectangularshots are abutted to and aligned with the adjacent rectangular shots toform a larger contiguous angled feature 404 comprising the mask pattern.Due to the forming of a contiguous angled feature 404, the angledfeatures 404 do not exhibit the loss of fidelity that was so apparent inFIG. 2 of the prior art. Rather, the angled features 404 exhibit welldefined, linear boundaries that make up its edges as shown in FIG. 6. Ifa negative resist is used, the unexposed regions of the resist may beremoved leaving the desired mask on the substrate. If a positive resistis used, the exposed regions may be removed leaving the desired mask onthe substrate. Such developing of the resist may be performed usingstandard techniques known in the art, such as subjecting the resist to asolvent.

Referring to the process flow diagram of FIG. 7, in another exemplaryembodiment, the orientation of the stage 17 supporting the substrate 18and the first aperture 30 and the second aperture 32 may or may not berelatively rotated with respect to each other by a predetermined anglein order to minimize the write time of the mask pattern. In act 702, thedesign data may be converted to the machine language used by theparticular EBL system. The central processing unit of the computer thatcontrols the EBL system determines, using a programmed algorithm,whether the time required to expose the angled features 404 usingmultiple stepped rectangular shots (as shown in FIG. 2) is greater thanor less than the time required to rotate the stage 17 or the firstaperture 30 and the second aperture 32 by an angle θ and subsequentlyform the angled features 404. The determination may be based, in part,on the number of angled features, the number of shots required to formthe angled features, and the time required for rotating the stage 17 orthe first aperture 30 and the second aperture 32. If the EBL systemdetermines that the write time to form the mask pattern is shorter ifthe angled features 404 are exposed on the resist without rotating thestage 17 or the first aperture 30 and the second aperture 32, then thestage 17 or the first aperture 30 and the second aperture 32 are notrotated. In such a case, in act 703, the angled and non-angled featuresare formed by exposing the resist to an electron beam shot-by-shot usinggenerally rectangular-shaped shots from the EBL system without rotatingthe stage 17 or the first aperture 30 and the second aperture 32. Thus,the angled features are exposed using multiple stepped or offsetgenerally rectangular-shaped shots forming the angled features as shownin FIG. 2.

If the programmed algorithm determines that the stage 17 or the firstaperture 30 and the second aperture 32 must be rotated to minimize thewrite time for producing the particular mask pattern, in act 704, thenon-angled features 402 may be formed by exposing the resist to anelectron beam shot-by-shot using generally rectangular-shaped shots fromthe EBL system. In an exemplary embodiment, following exposing of thenon-angled features 402, in act 706, the stage 17 supporting thesubstrate 18 may be rotated by an angle θ about a Z axis that isperpendicular to the surface of substrate 18 while the first aperture 30and the second aperture 32 remain stationary. In another exemplaryembodiment, following exposing of the non-angled features 402, in act706, the first aperture 30 and the second aperture 32 may be rotated byan angle θ about a Z axis that is perpendicular to the surface ofsubstrate 18 while the substrate 18 remains stationary. Control of therotation angle is effected in the same manner as in the previousembodiment, using the laser interferometer 28 or 28′. In act 708, theangled features 404 may be exposed by the EBL system. Since thesubstrate 18 or the first aperture 30 and the second aperture 32 hasbeen rotated, the angled features 404 are exposed by the EBL systemusing generally rectangular-shaped shots as if they were non-angledfeatures having all of the benefits of the previous embodiment, such as,reduced write time, and well defined, linear boundaries that make up theangled features 404 edges. If a negative resist is used, the unexposedregions of the resist may be removed leaving the desired mask on thesubstrate. If a positive resist is used, the exposed regions may beremoved leaving the desired mask on the substrate. Such developing ofthe resist may be performed using standard techniques known in the art,such as subjecting the resist to a solvent.

Although the foregoing description contains many specifics, these arenot to be construed as limiting the scope of the present invention, butmerely as providing certain exemplary embodiments. Similarly, otherembodiments of the invention may be devised which do not depart from thespirit or scope of the present invention. The scope of the invention is,therefore, indicated and limited only by the appended claims and theirlegal equivalents, rather than by the foregoing description. Alladditions, deletions, and modifications to the invention, as disclosedherein, which fall within the meaning and scope of the claims areencompassed by the present invention.

1. A method of forming a pattern on a resist comprising: providing asubstrate having a resist thereon; exposing the resist to at least onegenerally rectangular-shaped shot from an electron beam to form at leastone non-angled feature; rotating at least one of the substrate and apath of the generally rectangular-shaped shot; and exposing the resistwith at least one additional generally rectangular-shaped shot from theelectron beam to form at least one angled feature with at least onelinear, peripheral edge substantially oriented at a predetermined anglerelative to the at least one non-angled feature.
 2. The method accordingto claim 1, further comprising forming the at least one non-angledfeature using two or more generally rectangular-shaped shots from theelectron beam, wherein each generally rectangular-shaped shot is abuttedto an adjacent generally rectangular-shaped shot to form a largersubstantially contiguous feature.
 3. The method according to claim 2,further comprising forming the at least one angled feature using two ormore generally rectangular-shaped shots from the electron beam, whereineach generally rectangular-shaped shot is abutted to an adjacentgenerally rectangular-shaped shot to form a larger substantiallycontiguous feature.
 4. The method according to claim 1, furthercomprising developing the resist to form a mask on the substrate.
 5. Themethod according to claim 1, wherein t rotating at least one of thesubstrate and a path of the generally rectangular-shaped shot iseffected by rotating the substrate by a predetermined angle.
 6. Themethod according to claim 1, wherein rotating at least one of thesubstrate and a path of the generally rectangular-shaped shot iseffected by rotating an apparatus for defining the path of the generallyrectangular-shaped shot by a predetermined angle.
 7. The methodaccording to claim 1, wherein exposing the resist to at least onegenerally rectangular-shaped shot from an electron beam comprisespassing the electron beam through a blanking electrode to form the atleast one generally rectangular-shaped shot.
 8. The method according toclaim 7, further comprising passing the electron beam having the atleast one generally rectangular-shaped shot through an aperture to format least one smaller generally rectangular-shaped shot.
 9. The methodaccording to claim 1, wherein exposing the resist to at least onegenerally rectangular-shaped shot from an electron beam to form at leastone non-angled feature comprises converging the at least one generallyrectangular-shaped shot on the resist.
 10. A method of forming a patternon a resist comprising: providing a moveable stage including a substratehaving a resist thereon; directing an electron beam toward the resist;converging the electron beam on the resist to form at least onenon-angled feature; rotating at least one of the moveable stage and apath of the electron beam; and exposing the resist to at least onegenerally rectangular-shaped shot from the electron beam to form atleast one angled feature.
 11. The method according to claim 10, whereinconverging the electron beam on the resist to form at least onenon-angled feature comprises forming the at least one non-angled featureby exposing the resist to an electron beam shot-by-shot using generallyrectangular-shaped shots from the electron beam.
 12. The methodaccording to claim 10, further comprising storing design data for anintegrated circuit in a storage device coupled to a processor thatcontrols the electron beam and the moveable stage.
 13. The methodaccording to claim 12, further comprising converting the design datainto machine language used by the processor.
 14. The method according toclaim 10, further comprising forming the at least one non-angled featureusing two or more generally rectangular-shaped shots from the electronbeam, wherein each generally rectangular-shaped shot is abutted to anadjacent generally rectangular-shaped shot to form a largersubstantially contiguous feature.
 15. The method according to claim 10,further comprising forming the at least one angled feature using two ormore generally rectangular-shaped shots from the electron beam, whereineach generally rectangular-shaped shot is abutted to an adjacentgenerally rectangular-shaped shot to form a larger substantiallycontiguous feature.
 16. An electron beam lithography system comprising:a moveable electron gun configured to emit an electron beam; anapparatus for defining a shape of the electron beam; a moveable stageconfigured to support a substrate and located in a path of the electronbeam; a controller coupled to at least one the moveable electron gun andthe moveable stage.
 17. The electron beam lithography system of claim16, wherein the moveable stage stage is rotatable about an axissubstantially perpendicular to a plane of the stage.
 18. The electronbeam lithography system of claim 16, further comprising a laserinterferometer for determining the at least a rotational position of thestage.
 19. The electron beam lithography system of claim 16, wherein theapparatus for defining the shape of the electron beam is rotatable andoperably coupled to the controller for controlling at least a rotationalposition thereof.
 20. The electron beam lithography system of claim 16,further comprising a drive for effecting the rotation of the apparatusfor defining the shape of the electron beam therethrough.
 21. Theelectron beam lithography system of claim 16, wherein the apparatus fordefining the shape of the electron beam is rotatable and operablycoupled to the controller for controlling at least a rotational positionthereof.